The reactions of ketene thioacetals of general structures 6 and 9 with a number of electrophilic reagents are described. The reagents examined included thiocyanogen, positive bromine and chlorine sources, 2,4-dinitrobenzenesulfenyl chloride, p-nitrobenzenediazonium fluoroborate, diethyl azodicarboxylate, and chlorosulfonyl isocyanate. All reactions proceeded with substitution of the electrophile for the vinyl proton with retention of the ketene thioacetal skeleton. Ketene thioacetals 9a-c were converted to thioacetals of aldehydes by a protonation-hydride transfer process using organosilicon hydrides in acidic media as a key step in an aldehyde homologation sequence. The reactions of ketene thioacetals under these conditions involve cationic intermediates stabilized by electron donation from sulfur.